1. Field
One embodiment of the present invention relates to a disk drive and more particularly, to a frictional characteristics measuring technique in a contact recording system.
2. Description of the Related Art
In a disk drive such as a magnetic disk drive represented by a hard disk drive (HDD), in order to improve the recording density, it is necessary to make the flying height of the magnetic head as small as possible. However, as the flying height has already entered the zone of 10 nm or less, it is becoming more difficult to further reduce the flying height while also securing a margin for other variables. Against the background of these circumstances, a contact recording system in which a magnetic head and magnetic disk are in continuous sliding contact with each other was proposed some time ago.
Compared with the conventional HDD using a floating type slider, in which air pressure is utilized, in contact recording, in order to ensure stable recording/reproduction and a long lifespan, it becomes an essential task to avoid the state of excessive adhesion between the magnetic head and magnetic disk, stick-slip state, and jumping state, and reduce abrasion. For such purpose, it is necessary to keep the friction state in a desirable state by continuously monitoring the frictional characteristics inside the disk drive, and controlling the pressing load, and to issue, when a range of a certain variable is exceeded, an alarm to a host system.
One of the tasks/problems of frictional characteristics measurement is that an attraction force, such as the meniscus force or intermolecular force, acts between the magnetic head and magnetic disk in addition to the pressing load applied by the suspension or the like, hence the true friction coefficient cannot be obtained by simply measuring the in-plane force.
Further, to date, a method for accurately measuring the in-plane force in a disk drive has not been forthcoming. In general, when it is attempted to measure the frictional force with a high degree of sensitivity by using a sensor or the like, it is necessary to cause displacement in the direction of the frictional force by applying a force with a certain degree of springiness, and hence it is necessary to provide a part lower in rigidity than the periphery thereof. In a disk drive, when a part lower in rigidity is provided in the sliding direction of the magnetic disk, variations in the write or read signal in the time-axis direction are caused, and hence accurate read/write is disturbed.
The relational matter is disclosed in the prior art, for example Japanese Patent Application No. 10-235544 (Jpn. Pat. Appln. KOKAI Publication No. 2000-65720).